// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

// Writing to Windows Event Log requires the registry entries below to be present, with the
// following modifications:
// 1. <log_name>    should be replaced with your log name (e.g. your application name)
// 2. <source_name> should be replaced with the specific source name and the key should be
// duplicated for
//                  each source used in the application
//
// Since typically modifications of this kind require elevation, it's better to do it as a part of
// setup procedure. The snippet below uses mscoree.dll as the message file as it exists on most of
// the Windows systems anyway and happens to contain the needed resource.
//
// You can also specify a custom message file if needed.
// Please refer to Event Log functions descriptions in MSDN for more details on custom message
// files.

/*---------------------------------------------------------------------------------------

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\<log_name>]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\<log_name>\<source_name>]
"TypesSupported"=dword:00000007
"EventMessageFile"=hex(2):25,00,73,00,79,00,73,00,74,00,65,00,6d,00,72,00,6f,\
  00,6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,\
  5c,00,6d,00,73,00,63,00,6f,00,72,00,65,00,65,00,2e,00,64,00,6c,00,6c,00,00,\
  00

-----------------------------------------------------------------------------------------*/

#pragma once

#include <spdlog/details/null_mutex.h>
#include <spdlog/sinks/base_sink.h>

#include <spdlog/details/windows_include.h>
#include <winbase.h>

#include <mutex>
#include <string>
#include <vector>

namespace spdlog {
namespace sinks {

    namespace win_eventlog {

        namespace internal {

            struct local_alloc_t
            {
                HLOCAL hlocal_;

                SPDLOG_CONSTEXPR local_alloc_t() SPDLOG_NOEXCEPT : hlocal_(nullptr) {}

                local_alloc_t(local_alloc_t const&) = delete;
                local_alloc_t& operator=(local_alloc_t const&) = delete;

                ~local_alloc_t() SPDLOG_NOEXCEPT
                {
                    if (hlocal_)
                    {
                        LocalFree(hlocal_);
                    }
                }
            };

            /** Windows error */
            struct win32_error : public spdlog_ex
            {
                /** Formats an error report line: "user-message: error-code (system message)" */
                static std::string format(std::string const& user_message, DWORD error_code = GetLastError())
                {
                    std::string system_message;

                    local_alloc_t format_message_result{};
                    auto format_message_succeeded =
                        ::FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                                         nullptr,
                                         error_code,
                                         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                                         (LPSTR)&format_message_result.hlocal_,
                                         0,
                                         nullptr);

                    if (format_message_succeeded && format_message_result.hlocal_)
                    {
                        system_message = fmt_lib::format(" ({})", (LPSTR)format_message_result.hlocal_);
                    }

                    return fmt_lib::format("{}: {}{}", user_message, error_code, system_message);
                }

                explicit win32_error(std::string const& func_name, DWORD error = GetLastError()) : spdlog_ex(format(func_name, error)) {}
            };

            /** Wrapper for security identifiers (SID) on Windows */
            struct sid_t
            {
                std::vector<char> buffer_;

            public:
                sid_t() {}

                /** creates a wrapped SID copy */
                static sid_t duplicate_sid(PSID psid)
                {
                    if (!::IsValidSid(psid))
                    {
                        throw_spdlog_ex("sid_t::sid_t(): invalid SID received");
                    }

                    auto const sid_length{::GetLengthSid(psid)};

                    sid_t result;
                    result.buffer_.resize(sid_length);
                    if (!::CopySid(sid_length, (PSID)result.as_sid(), psid))
                    {
                        SPDLOG_THROW(win32_error("CopySid"));
                    }

                    return result;
                }

                /** Retrieves pointer to the internal buffer contents as SID* */
                SID* as_sid() const { return buffer_.empty() ? nullptr : (SID*)buffer_.data(); }

                /** Get SID for the current user */
                static sid_t get_current_user_sid()
                {
                    /* create and init RAII holder for process token */
                    struct process_token_t
                    {
                        HANDLE token_handle_ = INVALID_HANDLE_VALUE;
                        explicit process_token_t(HANDLE process)
                        {
                            if (!::OpenProcessToken(process, TOKEN_QUERY, &token_handle_))
                            {
                                SPDLOG_THROW(win32_error("OpenProcessToken"));
                            }
                        }

                        ~process_token_t() { ::CloseHandle(token_handle_); }

                    } current_process_token(::GetCurrentProcess());  // GetCurrentProcess returns pseudohandle, no leak here!

                    // Get the required size, this is expected to fail with ERROR_INSUFFICIENT_BUFFER and return
                    // the token size
                    DWORD tusize = 0;
                    if (::GetTokenInformation(current_process_token.token_handle_, TokenUser, NULL, 0, &tusize))
                    {
                        SPDLOG_THROW(win32_error("GetTokenInformation should fail"));
                    }

                    // get user token
                    std::vector<unsigned char> buffer(static_cast<size_t>(tusize));
                    if (!::GetTokenInformation(current_process_token.token_handle_, TokenUser, (LPVOID)buffer.data(), tusize, &tusize))
                    {
                        SPDLOG_THROW(win32_error("GetTokenInformation"));
                    }

                    // create a wrapper of the SID data as stored in the user token
                    return sid_t::duplicate_sid(((TOKEN_USER*)buffer.data())->User.Sid);
                }
            };

            struct eventlog
            {
                static WORD get_event_type(details::log_msg const& msg)
                {
                    switch (msg.level)
                    {
                    case level::trace:
                    case level::debug:
                        return EVENTLOG_SUCCESS;

                    case level::info:
                        return EVENTLOG_INFORMATION_TYPE;

                    case level::warn:
                        return EVENTLOG_WARNING_TYPE;

                    case level::err:
                    case level::critical:
                    case level::off:
                        return EVENTLOG_ERROR_TYPE;

                    default:
                        return EVENTLOG_INFORMATION_TYPE;
                    }
                }

                static WORD get_event_category(details::log_msg const& msg) { return (WORD)msg.level; }
            };

        }  // namespace internal

        /*
 * Windows Event Log sink
 */
        template <typename Mutex> class win_eventlog_sink : public base_sink<Mutex>
        {
        private:
            HANDLE hEventLog_{NULL};
            internal::sid_t current_user_sid_;
            std::string source_;
            DWORD event_id_;

            HANDLE event_log_handle()
            {
                if (!hEventLog_)
                {
                    hEventLog_ = ::RegisterEventSourceA(nullptr, source_.c_str());
                    if (!hEventLog_ || hEventLog_ == (HANDLE)ERROR_ACCESS_DENIED)
                    {
                        SPDLOG_THROW(internal::win32_error("RegisterEventSource"));
                    }
                }

                return hEventLog_;
            }

        protected:
            void sink_it_(const details::log_msg& msg) override
            {
                using namespace internal;

                bool succeeded;
                memory_buf_t formatted;
                base_sink<Mutex>::formatter_->format(msg, formatted);
                formatted.push_back('\0');

#ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
                wmemory_buf_t buf;
                details::os::utf8_to_wstrbuf(string_view_t(formatted.data(), formatted.size()), buf);

                LPCWSTR lp_wstr = buf.data();
                succeeded = static_cast<bool>(::ReportEventW(event_log_handle(),
                                                             eventlog::get_event_type(msg),
                                                             eventlog::get_event_category(msg),
                                                             event_id_,
                                                             current_user_sid_.as_sid(),
                                                             1,
                                                             0,
                                                             &lp_wstr,
                                                             nullptr));
#else
                LPCSTR lp_str = formatted.data();
                succeeded = static_cast<bool>(::ReportEventA(event_log_handle(),
                                                             eventlog::get_event_type(msg),
                                                             eventlog::get_event_category(msg),
                                                             event_id_,
                                                             current_user_sid_.as_sid(),
                                                             1,
                                                             0,
                                                             &lp_str,
                                                             nullptr));
#endif

                if (!succeeded)
                {
                    SPDLOG_THROW(win32_error("ReportEvent"));
                }
            }

            void flush_() override {}

        public:
            win_eventlog_sink(std::string const& source, DWORD event_id = 1000 /* according to mscoree.dll */) : source_(source), event_id_(event_id)
            {
                try
                {
                    current_user_sid_ = internal::sid_t::get_current_user_sid();
                }
                catch (...)
                {
                    // get_current_user_sid() is unlikely to fail and if it does, we can still proceed
                    // without current_user_sid but in the event log the record will have no user name
                }
            }

            ~win_eventlog_sink()
            {
                if (hEventLog_)
                    DeregisterEventSource(hEventLog_);
            }
        };

    }  // namespace win_eventlog

    using win_eventlog_sink_mt = win_eventlog::win_eventlog_sink<std::mutex>;
    using win_eventlog_sink_st = win_eventlog::win_eventlog_sink<details::null_mutex>;

}  // namespace sinks
}  // namespace spdlog
